F is for... Fitzwilliam

In March 2015 Sir Ranulf Fitzwilliam and his wife, the Lady Isabella, played host to a visit by King John at their castle, a day's ride from London. Travelling with the King was the French knight Sir Gilles Estram. He and Sir Ranulf's headstrong son Hugh had a falling out, which led to the young man being challenged to a duel. They would meet on the jousting field the next day. The Frenchman gained the upper hand, and was about to kill Hugh when the proceedings were interrupted by the TARDIS materialising. The King seemed bemused by the new arrivals - dubbing them his "demons" - and they were invited into the castle. The Doctor was concerned by John's presence, as he should have been in London on this date, taking the Crusaders oath. Sir Ranulf was also concerned, as the King was demanding more money from him and accusing him of being disloyal. The truth was revealed when Sir Ranulf's cousin arrived, claiming to have just left the King in London. Sir Gilles was really the Master in disguise (never!), and the King the android Kamelion, which could alter its appearance to match what its controller willed upon it. The false King had Isabella and Hugh locked in the dungeons, but the Master released them, in order to get the family on his side and against the Doctor. The Doctor and his companions stole Kamelion and fled in the TARDIS - convincing the Fitzwilliams' that they really had been visited by demons.

Played by: Frank Windsor (Sir Ranulf), Isla Blair (Lady Isabella), and Christopher Villiers (Hugh). Appearances: The King's Demons (1983).

• Windsor was best known for working his way up the police ranks in Z-Cars, Softly, Softly and Softly, Softly: Taskforce. He would return to Doctor Who in 1989 - as a policeman - in Ghost Light.
• Villiers returned to the programme more recently, playing Prof. Moorhouse in Mummy on the Orient Express.
• Isla Blair is married to Julian Glover, who played King John's brother Richard in the 1965 Doctor Who story The Crusade. Their son, Jamie, played Ian Chesterton actor William Russell in the drama about Doctor Who's origins - An Adventure in Space and Time - in 2013.